A communication service that uses an MIMO technique, such as WiMAX (Worldwide Interoperability for Microwave Access), is now about to begin. The MIMO technique is a technique that receives a plurality of electric waves passed through a plurality of propagation paths so as to improve transmission rate and communication quality. In this technique, it is preferable to use two or more antennas and to reduce correlation between two antennas used in order to obtain a large effect.
An antenna having the following features is the most suitable for use as a terminal of a communication service using the WiMAX technique: having antenna elements with different polarizations to thereby reduce correlation between the antenna elements; having an omnidirectional radiation pattern to thereby receive a large number of multiply reflected waves effective for the MIMO; and having a compact size.    Patent Document 1: JP-A-2003-347822    Patent Document 2: JP-A-2005-167705    Patent Document 3: JP-A-07-086825    Patent Document 4: JP-A-09-064639    Patent Document 5: JP-A-10-107533